Today is last date of Rcom cdma network. While customers in some places are already not receiving any signal on their cdma handset from past 2-3days.
Customers who have gone through sim upgrade process would have already received the sms regarding the sim activation. 
Some users are complaining not able to access data on Rcom 3G network if present in your circle. Here is process to avail the data service on Rcom 3G network using rcom 4G sim
1. Insert sim in a GSM handset
2. Got to settings & select manual network search
3. Select Reliance 3G
4. Also select the National Roaming option
5. Select the data services
6. Display will show R for somewhat unknown reasons.
7. Enjoy the services.
In meanwhile Rcom 4G services will be activated within next 3 to 7 days. Though Rcom customer care is not confirming anything about it. In meantime if you faceany problem then please reply here